Cooling of turbine rotors



April 16, 1957 J. A. FLINT COOLING OF TURBINE ROTORS Filed Feb. 14, 1952 ii a mla [nventqr 9-4.. ?M m m M ,uAttorney;

2,788,951 CooLING F TURBlNE ROTORS john Avery Flint, Cove, Farnborough, England, assignor to Power Jets (Research and Development) Limited,

London, England, a British company I Application February 14, 1952, Serial No. 271,582

Claims priority, application Great Britain February 15, 1951 4 Claims. (Cl. 253-3915) This invention relates to the cooling of those partse. g. the blades-of the rotors of multi-stage axial flow turbines and in particular of gas turbines, which are heated by the hot working fluid. The invention is particularly applicable where the rotor is a hollow structure partitioned into an axially successive series of separate chambers each independently communicating with the blading of a different turbine stage, and separate supplies of coolant are provided to the interior of these separate chambers.

Broadly, according to the invention, separate streams of coolant admitted to the turbine interior and led separately to the different rings of blading, pass along the rotor by separate concentric paths having the rotor axis as their common axis. According to one form of the invention the rotor is mounted on shafting, including a tube Within a hollow main shaft, so that independent paths are provided for supplies of coolant through the tube to one stage of the turbine and through one or more spaces between the tube and the wall of the bore of the main shaft to another stage of the turbine. Thus the bore of the main shaft may be of larger diameter than the outside of the inner shaft or the bore may be internally longitudinally grooved. As an addition to these concentric paths or as an alternative to one of them, the main shaft may also have external grooves forming another concentric path for coolant going to another stage of the turbine. If the rotor has three stages, the tube may supply the third stage, the annular internal space or internal grooves, the second stage, and the external grooves may supply the first stage.

The invention is intended to be applicable in particular, but not exclusively, to the turbine rotor cooling arrangement forming the subject matter of co-pending United States patent application Serial No. 271,601, filed February 14, 1952.

The invention makes it possible in certain cases to supply all the separate streams of coolant from one end of the turbineviz. the opposite end from that from which the drive is taken to the load.

One particular construction according to the invention is shown in the accompanying drawings of which Figure l is a longitudinal section through the upper part of a three-stage gas turbine and Figure 2 is a cross section on the line AA of Figure 1. In this construction the three-stage rotor is built up of three disc-like members or wheels 1, 2 and 3, each having a central hub and peripheral flange carrying conventional blades 4, the flanges of adjacent wheels being secured together in some well-known manner as for example by screwed joints 5 and 6. To one side of each ring of the rotor blades 4 is a ring of stator guide vanes 7 carried by the stator casing 8. The rotor is supported by a main shaft which comprises stub shaft 9 formed on wheel 1 and by another stub shaft 10 formed on wheel 3 and mounted in bearings 11 and 12 at opposite ends of the rotor; these bearings are supported by the stator casing 8.

Wheel 1 and its stub shaft 9 have an axial bore. The

United States Patent C wheel flanges where secured together at 5 and 6 are sealed together to close up each of the spaces between the webs of the wheels. Secured to a face of wheel 1 and rotating therewith, between the wheel and the bearing, is an annular enclosure member 13 also formed as a disc wheel with a rim abutting, at one edge, against the rim of the turbine wheel 1. The spaces between wheel 1 and enclosure member 13, between wheels 1 and 2 and between wheels 2 and 3 constitute separate air chambers 14, 15 and 16. Thus the wheels together constitute a rotor partitioned into an axially successive series of separate air chambers 14, 15 and 16. Holes 1a, 2a and 3a through the flanges of wheels 1, 2 and 3 put chambers 14, 15 and 16 into communication with cavities 17, 18 and 19 under the roots of blades 4 which are hollow for flow of coolant in a well-known manner.

Separate paths for cooling gas (hereinafter called air) are provided longitudinally along the rotor from the end supported by hearing 11 into the chambers 14, 15 and 16. For this purpose a tube 20 has its inner end fitting into the bore of wheel 2 to form the passage for coolant to chamber 16 to cool the third stage, this tube 20 passing. through the axial bore in the stub shaft 9 with such a considerable clearance space over a part of its length as to provide an annular passage 21 to admit coolant to chamber 15 for cooling the second stage of the turbine.

Fitting on and firmly secured to the outside of stub shaft 9 is a sleeve 22 which forms a journal seating for roller bearing 11a supported in the bearing housing forming part of stator casing 8. Extending along theoutside of stub shaft 9 and equally spaced therearound are several grooves 9a which alternate with splines 9bfitting in the sleeve 22, these grooves forming passages for a third stream of coolant to chamber 14 for cooling the first stage. Hollow stub shaft 9 extends through the bearing 11. The main shaft further comprises a hollow shaft extension piece 23 spigotted to stub shaft 9 which extends some distance further beyond the bearing; the cooling tube 20 passes right through the extension 23 and fits in and is secured thereto at its outer end. The grooves 9a in the external surface of the stub shaft 9 extend up to and are continued in the face of the hub of the wheel 1 wherein at 9c they curve smoothly from the axial to the radial direction.

The bearing end cap 24 on the end of the bearing housing is formed with an annular cavity 24a surrounding the shaft extension 23. The tubular wall of the main shaft is apertured by holes 23:: in the shaft extension 23 and these holes put cavity 24a into communication with the annular passage 21 around tube 20. The end cap 24 has also a second annular cavity 240 surrounding the internal cavity 240 in end cap 24 shows the tube 20, the

annular passage 21, the stub shaft 9 with grooves 9a and the sleeve 22. The view also shows that the end cap 24, where it includes the cavity 240, is provided with a boss 24b tapped to receive the coolant supply pipe and forming a tangential inlet for leading cooling fluid into the cavity 240 tangentially in a sense to give the incoming fluid a swirl in the direction of rotation of the stub shaft 9. The end cap 24 is also similarly formed around the internal cavity 24a.

The stub shaft 10 passes through the bearing 12 and extends outside as the driving shaft from which power can be taken. Thus it will be seen that all three streams of coolant can be admitted at the end of the turbine opposite from the end supported by bearing 12 and from which the power is taken. The bearing 12, which is shown only in external view, contains the usual journal and thrust bearings, all of which are of well-known form.

3 A disc like member 29 with a number of radial ribs is fastened to the 'leffhand facebf the turbine wheel 1 by being 'elamped between that-wheel-=and=themember 13;" A similar member 29 is clamped between wheels 1' and 2 and another between wheels Land 3. These members 29 fibrin enclosures and radiaipassages the chant-' befs' ;-='-and l'6 which izidia? passages aredined with; polished sheet metal spaced froiii tli'ef walls bers to form lieafinsulating air gapsi 1 m 'The'ri'in' of enclosiirehiembe'r 1 '3' 'eo-operates with an 10 annular stationary shroud 26 irou'nd fthe inside Ofthe first iing offstawr nozzle b1adesto "fornr a labyrinth seal 3ii topreventleakage bftlie hoFworking gases from the gas pathF- Th'i seal, being at the opposite end of are rotor' froni the thriist bearingi'isformed to extend l5 in a general direction nearly parallelto' the tui'bine shaft: axis-j so -that i twill allow"offtheconsiderablepossible reia'tiva movement due to" difieieiices ot ex'p'ansion bf" the-rotor and s'tator as theturbine'warnisiup to its working-temperature. Wtthe other e'ndlof theturbiiie, near" to the thrust bearing,'relativeinovement will bels'o' smalt" that a sealiil can 'be formed between the faces of rotary member and stationary riiernber'28 with' its gen'eral direction substantially radial. "Axial adjustment of the" rotorto adjust the spacing of this 'radialsal' will b" readily accommodated'by relative movement of theaxial' 'Forcooiing the turbine, in operation, one stream of air is le'dfinto the' end of the exteiiSibdZS and s6 into the openend of tube 29,whence"it'fl6ws into a'ir'chamber 16,throi1gh the radial pas's'ag's, and soto the blading of the third stage. "A'seco'zidstreaiii'ofi'air is'supplied; into cavity 244' and thenc'e 'thi'oug li the annular passage" 21-to the air chamber 1'5 and sets the blading of the second stage? A'third stream of air is supplied to cavity stagl" What I claim is:

1. gas turbine having a stator, a chambered bladed 40 rotor, a hollow shaft on said rotor comr riunicatingwith the interior 'of said rotor, 'holes' being provided through thewall'of said hollow shaft into its interior, anda membenforihed firstly with a' cavityfwhich encircles, in the shape of an annulus, the portion of the hollow shaft by groovesiin one of these said sleeve and shaft--ele-"-- 4 ments and communicating with the interior of the rotor, and a stationary member formed with a cavity which encirclesrin the"shapeof an annulus; the 'shaft afthe'" inlet end of said grooves, the member also having a coolant fluid inlet to said cavity whose direction is generally tangential to the annulus, the annulus and said coolant fluid inlet together-defining a fluid swirl path in the direction --of rotation-of thehollow shaft 3. A three-stage axial-flow gas turbine consisting of a stator;'a'chariiberediotorihaving'bladiiig ther ob rotor-being iiite rhally partitioned intcf an'aXia cessive series of separa'techamb'eis' each communicating with the blading of-a separate stage through: apertures in the peripheral surface of said rotor, at driving shaft extending from one ehd 'o'f the rotor," a" firstbearing sup,- porting said driving shaft, ahollow shaft on the other mid of said rotor, With'itsinteribr communicating with at least one of said chambers in the middle of the series, a tube extending axially through said hollow shaft with some clearance space therearou'nd, one end of said tube; communicating with at least the-one of said chambers nearest to said first bearing; an aperturedwall" terminat-i ing said clearance space towards the other end of said' tube'and defining a coolant fiuid'inlet to said clearance space, a bearing sleeve fitting concentrically around saidi hollow shaft a second bearingsupporting saidsleevey there being a plurality of axiallyextending passages: formed between said hollow shaft and said sleeve by grooves in one of these said sleeves and shaft elements and communicating with at least thefone of said-chambers nearest to saidgsecond bearing and means defininga 'separateinleffor coolant to said grooves;

'4. A gas turbine according to'claim-l'l'), including a member attached to saidsecond -bearing"and-:-havihg-" therein a first cavity extending around *sa'id-ho'llo'w shaft References Cited in the tile of this patent UNITED TATES PATENTS l,820,725 Bailey" l' Au 25, 1931' 7 1,3 0,747 Bowen ot. 4; 1932 1,938,688; Brooke" Decfl 2,1933 2,339,779 f" iibizwarth Ja'ni 2 5,; 1944' 2,575,6 2 Price lll; Nov. 20; 1951*" 2,611,532 Lju'n'gstrom s 'tlzsj; 1932 2,651,901 McLeod istqv. 351953 

